Electric cutout with lightning protection



Sept. 16, 1941. R. s. BENNETT 2,256,232 ELECTRIC CUTOUT WITH LIGHTNI NGPROTECTION v Filed Jan. 13, 1959 Fig. 1.

Ifiventor: Falph 5. Bennett,-

HIS Attorneg.

Patented Sept. 16, 1941 ELECTRIC CUTOUT WITH LIGHTNING PROTECTION RalphSrBennett, Pittsileld, Mass., assignor to General Electric Company, acorporation of New York Application January 13, 1939, Serial No. 250,787

' 9 Claims.

The present invention relates to electric cutouts and more particularlyto improvements in protective equipment for fuse cutouts.

In some applications of fuse cutouts, troubles have been experiencedfrom flashovers ,between the open circuited terminals or contacts of thecutout due to lightning surges. For example, in an installation where afuse cutout is employed for transformer protection and is connected onthe line side of the lightning arrester employed with the transformer,blowing of the fuse link leaves the cutout unprotected and tends to format the line terminal of the cutout a reflecting point for lightningsurges. As a result of this there may occur flashovers between thecutout terminals. with danger of damage-t0, or even complete destructionof, the cutout casing or other insulating suppo This danger exists Ialso in cases where fuse cutouts are employed for line sectionalizing prposes and the circuit between the terminals is left open due to fuseoperation. Itis a principal object of the present invention to provide,in a fuse cutout, simple and economical, yet reliable, protective meansfor preventing flashover and damage to the cutout due to lightningsurges.

A more specific object .of the invention is the provision of a unitaryprotective assembly, ineluding a fuse and lightning protection meanstherefor, which may be substituted readily for an unprotected fuseassembly in an existing cutout installation without disturbance oralteration of the cutout support.

Other objects and the details of that which I consider to be novel andmy invention will become apparent from the following description and theclaims appended thereto, .taken in con- Junction with the accompanyingdrawing in which Fig. 1' shows an exemplary embodiment of the inventionas applied to a fuse cutout of the enclosed type, and Figs. 2 and 3 aresectional views along the line 2-2 and 3-3 of Fig. 1. Although theinvention is illustrated and will be. described herein as appliedparticularly to a cutout of the enclosed type, it is to be understoodthat the invention in its broader aspects is not limited to the detailslar form of cutout disclosed and is applicable also to cutouts of theopen type.

The cutout casing ll shown on the drawing is of a form well known in theart and heretofore commonly employed in cutoutinstallations-incorporating only a single fuse holder or disconnect isconstructed of porcelain or blade. This casing respectively of theparticuother suitableinsulation and is formed with electric creepage andgas barriers l I and I2. Mounted in the casing are upper and lowerterminal contacts it closed and claimed in my Patent 2,011,391, issuedAugu t 13, 1935, and assigned to the assignee of the present invention.Each element It has two sets of prongs designated l8 and I9. Prongs l9have lugs engaging recesses.

in the inner faces of the side walls of Casing It for supporting thecontact assembly. Prongs l8 serve as backing strips for the contactfingers of element l6 and serve also as latching fingers in a mannerwhich will become apparent hereinafter. The contact assembly includesalso a base member 2| secured to elements II and I! by rivets l1 andprovided with a clamping member 22 for securing to the contact assemblya line conductor or lead inserted through an opening 23 in the side wallof the casing. The open front of the casing is closed by means of a door25, of suitable insulation material, which is pivotally mounted at itslower end on removable studs 28 carried by projections at the lower endof the casing. The door has an eyelet handle 21 for manipulation thereofto and from closed position and has also barriers 28 arranged forcooperation with the barriers H and I2 of the easing.

On the inner face of door is mounted a protective assembly including afuse holder and ex-. pulsion gap interrupting device. The fuse holder isof a common form including an expulsion arcing tube 30, of insulation,having a contact sleeve 3| mounted on the upper end thereof. .Within thefuse holder is disposed a fuse link, generally designated 32, thebutton-head upper terminalof which is secured in place by a removablecap 38, and the lower cable extension 24 of which fuse link projects outof the lower end of tube Ill.

The expulsion gap interrupting device ha a double walled tube ofinsulation'upon the upper end of which is threaded a terminal can 36.Within this tube is disposed a rod electrode 31 having a buttonheadterminal 38 secured in placeby cap 38. A second electrode in the form ofa metallic sleeve 39 is disposed within and adjacent the lower end oftube 35. The electrodes?!-v and 39 are arranged in spaced relationshipas illustrated, so as to provide an arcing gap within and H respectivelyof the form dis-.

the tube 35, and the sleeve form of electrode 39 provides for dischargeof gases from the tube.

The upper ends of the fuse holder and the expulsion gap interrupter aresecured together and 3 over when the circuit isopen between its con- Itacts by reason of fuse operation.

With the arrangement described it is not essential to provide a gap inseries with the expulsion gap interrupter since, under normal operation,the fuse link is in the circuit so that the voltage across the terminalsof the gap is very low. Thus there is not the danger, present in someexpulsion gap interrupter installations, of creepage between the gapelectrodes with -rcsultant progressive carbonization of the tube twodevices in parallel juxtaposition. This clamp is secured to tube 35 andelectrically connected with sleeve electrode 39 by means of screws 3.The two tubes are maintained in properly spaced relationship by means ofa notched sleeve 4| sup-- ported on a thumb-screw 45 extending betweenand supported by downwardly projecting spaced extensions 46 of clamp 42.One end of thumbscrew 45 is provided with a flange M for clamping fuselink extension 34 to clamp 42.

The protective assembly just described is removably secured to the innerface ofdoor 21 by quick detachable means in the form of resilientmetallic clips 50 and Clip 50 is secured to the door adjacent the upperend thereof by means of molded-in inserts 52 and has an opening 53 forengagement with the terminal cap 33 on the fuse holder. Clip SlisU-shaped and is secured to the door adjacent the lower end thereof by amolded-in insert 55. The spaced resilient arms of clip 5| have knobs 55engageable with sockets in clamp Q2, as will be seen best from Fig. 3,to latch the lower end of the protective assembly to the door. Theprotective assembly is readily attached to the door by first of theinterrupter.

One of the important features of the arrangement in accordance with mypresent invention is that the tubes of the fuse and the expulsion gapinterrupter are supported in alinement parallel to the rear face of thedoor. By reason of this, the protective assembly is adapted to fit intostandard cutout casings originally designed for accommodation only of asingle fuse assembly. Thusit is possible to replace an unprotectedsingle fuse assembly with a new cover having attached thereto theprotective assembly hereinbefore described. Increased protection maythereby be secured with little additional expense since dismounting oralteration of the cutout casing or other support is not required.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In an electric cutout, the combination with an insulating supporthaving a pair of spaced inserting cap 33 into opening 53 in upper clip'50, soas to latch the upper end of the assembly, and then pressing thelower end of the assembly into latching engagement with lower clip 5i.Thus the clips 50 and 5t serve to hold the assembly securely in positionas shown.

When the door is closed, contact fingers it of the upper stationarycontact assembly engage the sides of contact sleeve 3!, as shown in Fig.2, to effect electric connection with the upper end of the protectiveassembly, and inwardly bent portions of prongs i8 engage the spacesbetween sleeve 3| and cap 36 to latch the upper end of the protectiveassembly in operative position. At the same time the contact fingers ofelement I6 and the prongs B8 of the lower stationary contact assemblyengage clamp 32 to effect electric connection with the lower end of theprotective assembly. Thus the circuit between the stationary contacts iscompleted through fuse link 32.

In case the fuse link blows upon excess current, the resultant opencircuit condition between the stationary contacts would render thecutout subject to fiashover between the stationary contacts due tolightning surges were it not for the provision of the expulsion gapinterrupter. However, with the arrangement of the present invention, theexpulsion gap interrupter provides an impulse current discharge pathbetween the stationary contacts and the terminals of the protectiveassembly. The spacing between the electrodes Zil and 39 is so arrangedthat breakdown of the gap therebetween will occur before flashoverbetween the stationary contacts or between external conductive parts ofthe protective assembly. Thus the cutout is at all times protected fromdamage due to flashline terminal contacts mounted thereon, and a fuseassembly carried by said support and including a fuse link electricallyconnected between said contacts; of an expulsion gap interrupterincluding an expulsion tube having spaced electrodes providing adischarge gap in the tube and having spaced terminals for saidelectrodes, means supporting said interrupter with its said terminals inelectric association respectively with said contacts, and meansincluding said terminals and electrodes operative to provide a lightningimpulse discharge path interconnecting said contacts by way of said gapand tube when the circuit be-,

tween the contacts is open due to rupture of said fuse link.

2. In an electric cutout, the combination with an insulating supporthaving a pair of spaced line terminal contacts mounted thereon, of anelectric protective assembly detachably mounted on said support andcomprising a pair of spaced terminals for connection respectively withsaid pair of contacts, a fuse electrically connected between saidterminals, an expulsion gap interrupter including an expulsion tubehaving spaced electrodes providing a discharge gap in ,the tube, commonsupporting means for said fuse and interrupter, and means cooperativewith said electrodes to provide a lightning impulse discharge pathinterconnecting said terminals by way of said gap and expulsion tubewhen the circuit between the terminals is open due to operation of saidfuse.

3. In an electric cutout, the combination with an insulating supporthaving a pair of spaced line terminal contacts mounted thereon, of anelectric protective assembly comprising a tubular fuse holder having afuse link therein, an expulsion gap interrupter including an expulsiontube having spaced electrodes providing a discharge gap in the tube,means common to said fuse holder and expulsion tube for detachablymounting the assembly on said insulating support, spaced terpulsion gapminals for said fuse link arranged for connection respectively with saidcontacts, and means connecting said electrodes respectively with saidterminals.

4. In an electric cutout, the combinationwith an insulating casinghaving a pair of spaced line terminal contacts therein and a door forthe casing, of an electric protective assembly supported on the innerside of said door and comprising spaced terminals for the assemblyarranged for connection respectively with said contacts, a fuseelectrically connected between said assembly terminals, an expulsion gapinterrupter including an expulsion tube having spaced electrodesproviding a discharge gap in the tube and having spaced terminals forsaid electrodes, which said electrode terminals are electricallyassociated respectively with said assembly terminals, and meansincluding said electrode terminals and electrodes operative to provide alightning impulse discharge path interconnecting said assembly terminalsby way of said gap and expulsion tube when the circuit between theassembly terminals is open due to operation of said fuse.

5. An electric protective unit comprising in combination, a door adaptedto close an open side of an electric cutout or like casing, a fuse, apair of spaced terminals for said fuse arranged for connectionrespectively with a pair of spaced contacts in a cutout or like casing,an expulsion gap interrupter including an expulsion tube having spacedelectrodes providing an arcing gap in the tube, means supporting saidfuse and interrupter on the inner side of said door, and meanscooperative with said electrodes to provide a lightning impulsedischarge path interconnecting said terminals by way of said gap andexpulsion tube.

6. An electric protective unit comprising in combination, a door adaptedto close an open side of an electric cutout or like casing, a fuse, anexinterrupter including an expulsion tube having spaced electrodesproviding an arcing gap in the tu means common to said fuse andinterrupter detachably supporting the fuse and interrupter on the innerside of said door, a pair of spaced terminals for engagementrespectively with a pair of spaced contacts in a cutout or like casing,means connecting said fuse between said terminals, and means connectingsaid electrodes respectively with said terminals.

7. An electric protective unit comprising in combination, a door adaptedto close an open side of an electric cutout or like casing, a tubularfuse holder having a fuse link therein, an expulsion gap interrupterincluding an expulsion tube having spaced electrodes providing an arcinggap in the tube, means clamping said holder and tube in non-coaxialsubstantially parallel juxtaposition to form a unitary assembly, meansdetachably securing said assembly to the inner side of said door, a pairof spaced terminals for said assembly arranged respectively to engage apair of spaced contacts in a cutout or like casing, means connectingsaid fuse link between said terminals, and means connecting saidelectrodes respectively with said terminals;

8. An electric protective unit comprising in combination, a door adaptedto close the open front of an electric cutout or like casing, a tubularfuse holder having a fuse link therein, an expulsion gap interrupterincluding an expulsion tube having spaced electrodes providing an arcinggap in the tube, spaced terminals for engagement respectively withspaced contacts in a cutout or like casing, means connecting said fuselink between said terminals, mean connecting said electrodesrespectively with said terminals, and means supporting said fuse holderand expulsion tube in non-coaxial substantially parallel extendingjuxtaposition on the inner side of said door with the axes of the holderand tube substantially in alignment in a plane perpendicular to the rearface of the door.

9. An electric protective unit comprising in combination, a firstcircuit interrupting device including a tubular insulating holder andconductive means therein operable to interrupt current flow in theholder, a second circuit interrupting device structurally separate anddistinct from said first device and including an expulsion tube havingspaced electrodes providing a surge gap in the tube, means common tosaid devices for supporting the same removably on an insulating support,and a pair of spaced terminals designed for engagement respectively withspaced contacts on such insulating support, which said terminals areelectrically connected respectively with the opposite ends of saidconductive means and also are electrically connected each with arespective one of said electrodes.

- RALPH S. BENNE'I'I'.

